A relational database management system stores relational tables, which are accessed by queries according to a standard database query language (such as the Structured Query Language or SQL). Examples of SQL statements include INSERT, SELECT, UPDATE, and DELETE. The SELECT statement is used to retrieve information from the database and to organize information for presentation to a user or an application program. The INSERT statement is used to insert a row (or multiple rows) into a table. The DELETE statement is used to delete a row (or multiple rows) from a table. The UPDATE statement is used to modify or change the content of the table. When a SQL query is received by a database system, a parser interprets the query statement, checks the statement for proper SQL syntax, and evaluates it semantically.
Some database systems are implemented as parallel database systems having a plurality of processor modules. Properly controlling execution of a database query in a parallel database system, particularly when anomalies are occurring, is typically very challenging. Usually, when anomalies occur, manual intervention by database administrators is often required to take appropriate actions in response to the anomalies. In a complex database system such as a parallel database system, manual intervention usually requires that a database administrator have extensive knowledge regarding the internal workings of the database system to properly identify anomalies and effect appropriate actions.